1. Field of the Invention
The present invention relates to electrophotography developing systems. More specifically, the present invention relates to image transfer processes and mechanisms in an electrophotography developing system.
2. Description of the Prior Art
Electrophotography developing systems are widely used in copying machines, laser beam printers, LPH (LED(Light Emitting Diode) print head) printers, paper facsimile machines and the like. Conventional electrophotography developing entails repeating a cycle of charging a medium, exposing and developing the medium, then transferring the image to another medium and fixing it thereto. Contact charging systems have been adapted widely to minimize generation of ozone that occurs during the charging operation.
Several types of electrophotography apparatuses are described in the patent literature. U.S. Pat. No. 5,166,734, for an Imaging System Including Pre-transfer Discharge to Pinhas et al., employs a photoconductive drum which is charged by a corotron. The image portions are discharged while the background portions remain at full charge. Referring to column 4, lines 39-44, a spray of liquid toner may be directed onto a portion of the roller 38 or onto a portion of photoconductive drum 10. Referring to column 5, lines 63-68, an intermediate transfer member 30 is maintained at a voltage and temperature suitable for electrostatic transfer of the image thereto. Referring to column 7, lines 20-26, the optimum transfer potential of the intermediate transfer member is -400 volts. The image transfer medium does not contain the surface having a positive charge.
U.S. Pat. No. 5,140,375, for an Image Forming Apparatus to Shindo et al., includes a brush which induces a bias voltage on a recording sheet. Referring to column 7, lines 59-65, the bias voltage induced on the sheet is controlled between 0.25 to 2.0K Volts and exhibits the same polarity as the toner.
U.S. Pat. No. 5,036,360, for a Moisture Compensation for Electrostatographic Apparatus to Paxon et al., induces an electrostatic charge of a predetermined primary voltage V.sub.o to the surface of a photoconductive belt. Referring to column 3, lines 26-30, the belt brings the areas bearing latent charge images into a development station 38. Referring to lines 33-38, charged toner particles on preselected magnetic brushes are attracted to the oppositely-charged latent image patterns on the belt.
I have noticed that the developing material that remains, that is, the non-transfer developing material, adheres to the photosensitive drum due to fatigue phenomenon common to photosensitive drums. This non-transferred developing material contaminates the next image to be transferred to the recording papers. Additionally, some of the non-transferred developing material is transferred to the transfer roll. Some of this residual developing material on the transfer roll subsequently is transferred to the rear surface of subsequent recording papers being developed, introducing unwanted latent images thereon.
I have found that the art represented by these exemplary references demonstrates a need for an electrophotography system which minimizes the contamination of recording papers with latent images due to the unwanted transfer residual developing material.